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Abstract:

This dataset contains vegetation survey data from an upland heath site in the Clocaenog Forest. This was done by pin point methodology, and data includes both pin hits as well as measurements converted into plant biomass (grammes per square metre). Vegetation was surveyed in the experimental plots at the Climoor site in 1998, 1999, 2000, 2002, 2003, 2007, 2008, 2009, 2010, 2011 and 2012. The vegetation at the site is a typical UK upland heathland, dominated by Calluna vulgaris, with Vaccinium myrtillus and Empetrum nigrum also being present in the vegetation understory. In each year, measurements were taken at a time period of maximum growth, which was late August/early September. Individual species can be examined, as well as the different components of the higher plants (i.e. leaf, stem, flower). Data was collected by CEH staff and PhD students trained in the use of the methods. Climoor is a climate change manipulation experiment that utilises automated roof technology to produce drought and warming experimental treatments that reflect climate change predictions for the next 20-30 years.

Method Description:

The vegetation biomass in the plots was surveyed in 1998, 1999, 2000, 2002, 2003, 2007, 2008, 2009, 2010, 2011 and 2012. In each year, measurements were taken in the same areas at a time period of maximum growth in late August/early September.
Within each plot, three quadrats (C7, D4 and F6; see Appendix 1 and 2) were chosen, and in each quadrat a grid of 100 pins were lowered through the multi-layered canopy. The pins were lowered onto a grid of 10 rows each with 10 pins in each of the 3 quadrats. Permanent base pegs that the point quadrat grid frames were mounted on were installed in each of the quadrats to ensure the same vegetation was surveyed each year. Every touch of vegetation was recorded, detailing the height of the hit, the species and the structure (i.e. leaf, stem, etc.). Multiple hits of the same species structure were only recorded once for each height (e.g. two V. myrtillus leaves touching at the same height would only be recorded once). Pin hits were recorded on dictaphones and transcribed back in the office into Excel. The transcribing stage is double checked to ensure no typos have been made in data input. This is done using a combination of the filter tool in excel to look for misspelt species codes and to check all the rows/pins for each quadrat are included.
The total number of pins recorded in each plot (should be 300) is double checked to make sure none have been missed and the total number of hits for each of the data input codes determined. The data are adjusted for any missing pins. This is done simply: if the number of pins deviates from the 300 that should have been recorded, each of the hit totals for each of the data input codes is adjusted by this ratio.
For example:
In plot 1 only 298 pins were recorded and 2 were missed. A conversion factor of 1.01 (ie 300/298) is calculated and applied to all the data input codes. For Calluna Green (CG), the number of hits recorded on the 298 pins was 612 in total. This is then multiplied by 1.01 to give 616.
Pin hits were then converted to biomass (g/m2) data using a biomass calibration-conversion. In 2000, 10 areas (each 0.5 m * 0.5 m) outside and surrounding the experimental plots were pin-pointed in an identical method to that carried out inside the plots, and then destructively harvested to determine calibration calculations between biomass and number of pin-hits. Table 6 gives the conversion factor between pin hits and the biomass of each plant species (bryophytes are pooled).